I recently aquired this aquarium from a customer for free and am going to try to use it for my bullfrog tadpoles when the metamorphize (not sure if that's a word). Just wanted to get some input. Here is a picture of it!

Any suggestions on how to get the hard water buildup off?

Another option is a terrarium I have that I could use and put another smaller aquarium inside for water. Here is a picture of it: